2. The mechanical equivalent heat: a) Using the table provided, what is the chan

Question

2. The mechanical equivalent heat: a) Using the table provided, what is the change in the thermistor resistance if its tem- perature rises from 21 C to 30 C? t2 5.Zim k Crouation G0), what is the temprtur n Cihe thermistor reistamne is KS2? c) Does it matter how many turns of cord surround the cylinder? Why? d) Does it matter how fast you turn the crank? Why? e) Suppose the cord, where it is attached to the post, is under tension during the exper- iment. Would this lead to an error in your measured value of the mechanical equivalent of heat? If so, would your value be too large, or too small?

Explanation / Answer

(a) the thermistor resistance drops by 41.388 Kile Ohms.

(b) Direct substitution of R = 125.74 in the given equation gives ,

T = 20+20.71+10.05+14.67

to get it in Celsius, add 273 to it, therefore final temperature = 65.43 + 273

(c) Yes, it matters, because the length of the cord wrapped determines the friction which then in turn determines the torque applied and hence in the final value of the resistance.

(d) Yes, it matters, coz the faster you crank the more revolutions and therefore gets more work done per turn. If turned quickly enough it can make the cord tension vanish.

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